JP2011104995A - Image erasing method and image erasing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image erasing apparatus and an image erasing method in which the laser beam scanning is required only in a uniaxial direction, the erasing at high speed with low energy is permitted and the significant reduction for apparatus cost is permitted. <P>SOLUTION: The image erasing apparatus includes: a semiconductor laser array; a width direction collimating means which is disposed on an output surface of the semiconductor laser array and is configured to collimate the broadening in the width direction of laser beams emitted from the semiconductor laser array; and a major axis length direction light distribution controlling means which is disposed on an output surface of the width direction collimating means, is configured to control a length of a major axis of the formed linear beam to be longer than the length of a beam source of the semiconductor laser array and to attain uniform light distribution in the length direction, wherein the linear beam which has the length of a major axis longer than the length of the beam source of the semiconductor laser array and uniform light distribution in the length direction is applied to a thermo-reversible recording medium in which any of transparency or color tone thereof reversibly changes depending on temperature, the thermo-reversible recording medium is heated and, thereby, an image recorded on the thermo-reversible recording medium is erased. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  In the present invention, a semiconductor laser (LD) array in which a plurality of semiconductor lasers (LD) are arranged in a straight line is converted into a highly uniform line beam by an optical lens, and the line beam is converted into a thermoreversible recording medium. The present invention relates to an image erasing method and an image erasing apparatus for erasing an image recorded by irradiation.

  To date, image formation and image erasure on a thermoreversible recording medium (hereinafter sometimes referred to as “recording medium” or “medium”) is a contact type in which a heating source is brought into contact with the recording medium to heat the medium. It is done in As the heat source, a thermal head is usually used for image formation, and a heat roller, a ceramic heater, or the like is used for image erasure.

  In such a contact-type recording method, when the thermoreversible recording medium is a flexible material such as a film or paper, uniform image formation and press can be performed by pressing the recording medium uniformly against a heating source with a platen or the like. There is an advantage that image erasing can be performed and an image forming apparatus and an image erasing apparatus can be manufactured at low cost by diverting components of a conventional thermal paper printer. However, when the thermoreversible recording medium incorporates an RF-ID tag or the like as described in Patent Documents 1 and 2, the thermoreversible recording medium becomes thicker and the flexibility is reduced and heating is performed. High pressure is required to press the source uniformly. In addition, because of the contact type, if printing and erasing are repeated, the surface of the recording medium is scraped to create irregularities, and a portion that does not come into contact with a heating source such as a thermal head or a hot stamp comes out and is not heated uniformly. There is a problem that erasure failure occurs (see Patent Documents 3 and 4).

  Furthermore, while reading and rewriting of stored information is performed from where the RF-ID tag is separated without contact, there is a demand for rewriting the image from a distant position on the thermoreversible recording medium. For example, a method using a laser has been proposed as a method for forming and erasing an image uniformly when irregularities occur on the surface of the thermoreversible recording medium or from a distant place (see Patent Document 5). This method describes that non-contact recording is performed using a thermoreversible recording medium on a transport container used in a distribution line, writing is performed with a laser, and erasing is performed with hot air, hot water, or an infrared heater. ing.

  As a recording method using such a laser, a laser recording device (laser marker) capable of irradiating a thermoreversible recording medium with a high-power laser beam and controlling its position is provided. Using this laser marker, it is possible to irradiate a thermoreversible recording medium with laser light, and the photothermal conversion material in the medium absorbs light and converts it into heat, and recording and erasing can be performed with the heat. Conventionally, as a method for forming and erasing an image with a laser, a method of recording with a near infrared laser beam by combining a leuco dye, a reversible developer, and various photothermal conversion materials has been proposed (see Patent Document 6). )

As a method for recording on a thermoreversible recording medium rewritable by near-infrared laser light, for example, non-contact rewriting by laser light is possible using a semiconductor laser (LD) light source.
A laser recording device (laser marker) that performs non-contact rewriting using a semiconductor laser requires a high output and a small circular beam in order to print small characters with thin lines at high speed. As described above, in order to convert a linear beam from the LD array 1 composed of a plurality of LD light sources into a circular beam, a fiber coupling LD including a special optical lens system 11 and an optical fiber 12 is used. However, the problem is that the higher the output of the laser beam and the greater the number of light sources of the LD array, the more complicated the special optical lens system 11 and the higher the device cost. In addition, the fiber-coupled LD has a lens system built in, and the LD light source cannot be directly cooled, so the cooling efficiency is low and it is difficult to increase the output, and it is a complicated optical system. However, it was difficult to increase the output because the efficiency was lowered.

In image recording, only the image recording portion is irradiated with the laser beam by the vector method, whereas in image erasing, the entire surface of the thermoreversible recording medium is irradiated with the laser beam. High output is required.
As an image erasing method using the laser recording apparatus, as shown in FIGS. 2A and 2B, there is proposed a method of erasing an image by scanning while overlapping in parallel using a circular beam of a normal laser marker. (See Patent Documents 7, 8, and 9).
However, these proposed methods have a problem that the cost of the apparatus increases in order to increase the output of the laser beam.

  On the other hand, in order to increase the output of the LD light source, if the output is increased by one light source, the LD light source element is damaged. Therefore, an LD element (LD array) equipped with a plurality of LD light sources is generally used. For example, in Patent Document 10, as shown in FIG. 3, laser light heating that converts laser light emitted from an LD array 1 in which a plurality of light sources are linearly arranged into band-like light by a first cylindrical lens 13 is disclosed. Tools have been proposed. In FIG. 3, reference numeral 14 denotes a second cylindrical lens 14 that condenses the strip-shaped parallel light emitted from the first cylindrical lens 13 in the width direction. However, in this proposal, there is no indication whether the strip-shaped light emitted from the first cylindrical lens 13 is uniform or not, and the second cylindrical lens 14 collects the light and corrects the soldering and soldering. Therefore, the configuration and the object are different from those of the present invention.

Further, in Patent Document 11, a line light source that arranges lenses for forming an image on an LD array in which a plurality of light sources are arranged to form band-like light with a uniform light distribution is used for a thermoreversible recording medium. On the other hand, it has been proposed to perform image recording and image erasing.
However, in this proposal, since the lens that forms an image with respect to each light source of the LD array is arranged, the apparatus becomes complicated, and the width of the light source of the LD array is the same as the width irradiated to the thermoreversible recording medium. There is a problem that the width of the light source of the LD array needs to be widened, resulting in an increase in apparatus size and a significant increase in apparatus cost.

  Further, Patent Documents 12 and 13 introduce an illumination device equipped with an optical lens configuration for forming a uniform light distribution, but for a thermoreversible recording medium capable of rewriting near-infrared laser light. There is no disclosure or suggestion of irradiating and repeatedly recording and erasing images.

  Therefore, at present, there is a demand for prompt provision of an image erasing apparatus and an image erasing method that enable high-speed erasing with low energy and can significantly reduce the apparatus cost.

  An object of the present invention is to solve various problems in the prior art and achieve the following objects. That is, according to the present invention, the scanning of the laser beam is only required in one axial direction, which is simpler than the scanning of the laser beam of the circular beam, enables high-speed erasing with low energy, and can greatly reduce the apparatus cost. An object is to provide an erasing apparatus and an image erasing method.

  As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, it is not necessary to use a circular beam for image erasing. Therefore, an optical lens using a linearly arranged LD array having a plurality of LD light sources is used. By converting into a linear beam, the laser beam can be scanned only in one axial direction, which is simpler than the laser beam scanning of a circular beam, enabling high-speed erasing with low energy, and greatly reducing the equipment cost. I knew that it would be possible.

The present invention is based on the above findings by the present inventors, and means for solving the above problems are as follows. That is,
<1> a semiconductor laser array in which a plurality of semiconductor laser light sources are arranged linearly;
A width direction collimating unit disposed on the emission surface of the semiconductor laser array and configured to parallelize the spread in the width direction of the laser beam emitted from the semiconductor laser array;
The long axis length of the linear beam formed by the width direction collimating means is longer than the long axis length of the light emitting part of the semiconductor laser array and has a uniform light distribution in the long axis length direction. A direction light distribution control means,
A linear beam having a light distribution that is longer than the long axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the long axis length direction is reversibly changed in temperature or transparency depending on temperature. An image erasing apparatus that erases an image recorded on a thermoreversible recording medium by irradiating and heating the reversible recording medium.
<2> A beam that adjusts at least one of the major axis length and minor axis length of a linear beam that is longer than the major axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the major axis length direction. The image erasing apparatus according to <1>, further including a size adjusting unit.
<3> The image erasing apparatus according to any one of <1> to <2>, wherein the width direction parallelizing unit is a cylindrical lens.
<4> The image erasing apparatus according to any one of <1> to <3>, wherein the long axis length direction light distribution control unit is a lens array.
<5> The image erasing apparatus according to any one of <1> to <4>, wherein the long axis length direction light distribution control unit is a Fresnel lens.
<6> Scanning means for scanning in a uniaxial direction a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and uniform in the major axis length direction on the thermoreversible recording medium. The image erasing apparatus according to any one of <1> to <5>.
<7> The image erasing apparatus according to <6>, wherein the scanning unit is a uniaxial galvanometer mirror.
<8> The image erasing apparatus according to <6>, wherein the scanning unit is a stepping motor mirror.
<9> The image erasing apparatus according to <6>, wherein the scanning unit is a polygon mirror.
<10> A thermoreversible recording medium is moved by a moving means with respect to a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and uniform in the major axis length direction. The image erasing apparatus according to any one of <1> to <9>, wherein the linear beam is scanned on a recording medium to erase an image recorded on the thermoreversible recording medium.
<11> The image erasing apparatus according to <10>, wherein the thermoreversible recording medium is attached to the surface of the container, and the thermoreversible recording medium is moved by moving the container by a moving unit.
<12> a width-direction parallelizing step for parallelizing the spread in the width direction of laser light emitted from a semiconductor laser array in which a plurality of semiconductor laser light sources are linearly arranged;
The long axis length of the linear beam formed in the parallelizing step in the width direction is longer than the long axis length of the light emitting portion of the semiconductor laser array and makes the light distribution uniform in the long axis length direction. Directional light distribution control process;
Comprising at least
A linear beam having a light distribution that is longer than the long axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the long axis length direction is reversibly changed in temperature or transparency depending on temperature. An image erasing method comprising erasing an image recorded on a thermoreversible recording medium by irradiating and heating the reversible recording medium.
<13> A beam that adjusts at least one of the major axis length and minor axis length of a linear beam that is longer than the major axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the major axis length direction. The image erasing method according to <12>, including a size adjustment step.
<14> A scanning step of scanning in a uniaxial direction a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and uniform in the major axis length direction on the thermoreversible recording medium. The image erasing method according to any one of <12> to <13>.
<15> A thermoreversible recording medium is moved by a moving unit with respect to a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and uniform in the major axis length direction. The image erasing method according to any one of <12> to <13>, wherein the line beam is scanned on the recording medium to erase the image recorded on the thermoreversible recording medium.

  According to the present invention, the conventional problems can be solved, and the laser beam can be scanned only in one axial direction, which is simpler than the laser beam scanning of a circular beam, and enables high-speed erasing with low energy, resulting in an apparatus cost. An image erasing apparatus and an image erasing method can be provided.

FIG. 1 is a diagram illustrating an example of a conventional image erasing apparatus. FIG. 2A is a diagram showing a conventional laser beam shape. FIG. 2B is a diagram showing a laser beam scanning method when a conventional beam shape is used. FIG. 3 is a diagram illustrating an example of a conventional laser beam heating tool. FIG. 4A is a schematic cross-sectional view showing an example of the layer structure of the thermoreversible recording medium of the present invention. FIG. 4B is a schematic cross-sectional view showing another example of the layer structure of the thermoreversible recording medium of the present invention. FIG. 4C is a schematic cross-sectional view showing still another example of the layer structure of the thermoreversible recording medium of the present invention. FIG. 5A is a graph showing the color-decoloring characteristics of the thermoreversible recording medium. FIG. 5B is a schematic explanatory diagram showing the mechanism of color development / decoloration change of the thermoreversible recording medium. FIG. 6 is a schematic view showing an example of the image erasing apparatus of the present invention. FIG. 7 is a schematic view showing another example of the image erasing apparatus of the present invention. FIG. 8 is a diagram showing a laser beam shape and a laser beam scanning method according to the present invention. FIG. 9 is a graph comparing the erasability due to the difference in the erasing method in the embodiment. FIG. 10 is a diagram for explaining jumps in laser beam scanning (laser beam scanning without laser beam irradiation). FIG. 11 is a schematic explanatory diagram illustrating an example of an RF-ID tag.

(Image erasing device and image erasing method)
The image erasing apparatus of the present invention comprises at least a semiconductor laser array, a width direction collimating means, and a long axis length direction light distribution control means, a beam size adjusting means, a scanning means, and further if necessary. It has other means.
In the image erasing apparatus of the present invention, a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the major axis length direction is controlled in transparency and color tone depending on the temperature. An image recorded on the thermoreversible recording medium is erased by irradiating and heating the thermoreversible recording medium, which either changes reversibly.
The image erasing method of the present invention includes at least a width direction parallelization step and a long axis length direction light distribution control step, and includes a beam size adjustment step, a scanning step, and other steps as necessary. Become.
In the image erasing method of the present invention, a linear beam having a light distribution longer than the major axis length of the light emitting portion of the semiconductor laser array and having a uniform light distribution in the major axis length direction is controlled in transparency and color tone depending on the temperature. An image recorded on the thermoreversible recording medium is erased by irradiating and heating the thermoreversible recording medium, which either changes reversibly.

  The image erasing method of the present invention can be preferably carried out by the image erasing apparatus of the present invention, the width direction parallelizing step can be performed by the width direction parallelizing means, and the major axis length direction light distribution. The control step can be performed by the long axis length direction light distribution control unit, the beam size adjustment step can be performed by the beam size adjustment unit, the scanning step can be performed by the scanning unit, Other steps can be performed by the other means.

<Semiconductor laser array>
The semiconductor laser array is a semiconductor laser light source in which a plurality of semiconductor lasers are linearly arranged, and preferably includes 3 to 300 semiconductor lasers, more preferably 10 to 100.
If the number of the semiconductor lasers is small, the irradiation power may not be increased. If the number is too large, a large-scale cooling device for cooling the semiconductor laser array may be required. In order to emit light from the semiconductor laser array, the semiconductor laser is heated and needs to be cooled, which may increase the cost of the apparatus.
The major axis length of the light emitting portion of the semiconductor laser array is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 mm to 50 mm, and more preferably 3 mm to 15 mm. If the major axis length of the light emitting portion of the semiconductor laser array is less than 1 mm, it may be impossible to increase the irradiation power. If it exceeds 50 mm, a large-scale cooling device for cooling the semiconductor laser array. May be required and the cost of the apparatus may increase.
Here, the light emitting portion of the semiconductor laser array means a portion that effectively and actually emits light in the semiconductor laser array.

The wavelength of the laser beam in the semiconductor laser array is preferably 700 nm or more, more preferably 720 nm or more, and further preferably 750 nm or more. The upper limit of the wavelength of the laser beam can be appropriately selected according to the purpose, but is preferably 1,500 nm or less, more preferably 1,300 mm or less, and further preferably 1,200 nm or less.
When the wavelength of the laser beam is shorter than 700 nm, there is a problem that in the visible light region, the contrast of the thermoreversible recording medium during image recording is lowered or the thermoreversible recording medium is colored. Furthermore, there is a problem that the thermoreversible recording medium is likely to deteriorate in the ultraviolet light region of a short wavelength. In addition, the photothermal conversion material added to the thermoreversible recording medium requires a high decomposition temperature in order to ensure durability against repeated image processing. When an organic dye is used for the photothermal conversion material, the decomposition temperature is high and the absorption wavelength is high. It is difficult to obtain a long photothermal conversion material. Accordingly, the wavelength of the laser beam is preferably 1,500 nm or less.

<Width direction parallelization step and width direction parallelization means>
The width direction parallelizing step is a step of forming a line beam by parallelizing the spread in the width direction of laser light emitted from a semiconductor laser array in which a plurality of semiconductor lasers are arranged in a straight line. Can be implemented.
The width direction parallelizing means is not particularly limited and may be appropriately selected depending on the purpose. For example, one single-sided convex cylindrical lens, a plurality of convex cylindrical lenses, a concave cylindrical lens, or these The combination etc. are mentioned.
The laser light of the semiconductor laser array has a larger diffusion angle in the width direction than in the length direction, and the width-direction paralleling means is disposed close to the emission surface of the semiconductor laser array, so that the beam width (short axis) (Length) can be avoided and the lens can be made small, which is preferable.

<Long axis length direction light distribution control step and long axis length direction light distribution control means>
In the long axis length direction light distribution control step, the long axis length of the line beam formed in the width direction parallelization step is longer than the long axis length of the light emitting portion of the semiconductor laser array, and the long axis length This is a step of making the light distribution uniform in the direction, and can be implemented by the long axis length direction light distribution control means.
The long axis length direction light distribution control means is not particularly limited and may be appropriately selected depending on the intended purpose. For example, two spherical lenses, an aspherical cylindrical lens (length direction), a cylindrical lens ( It can be realized by a combination of (width direction). Examples of the aspheric cylindrical lens (length direction) include a convex lens array, a concave lens array, and a Fresnel lens. The lens array refers to a lens in which a plurality of convex or concave lenses are arranged in the length direction. A uniform light distribution can be obtained by diffusing in the length direction with the aspherical cylindrical lens.
The long axis length direction light distribution control means is arranged on the exit surface side of the width direction parallelizing means.

<Beam size adjustment process and beam size adjustment means>
The beam size adjusting step includes a long axis length and a short axis of a linear beam having a uniform light distribution in the long axis length direction on the thermoreversible recording medium, which is longer than the long axis length of the light emitting portion of the semiconductor laser array. This is a step of adjusting at least one of the axial lengths, and can be performed by a beam size adjusting means.

The beam size adjusting means is not particularly limited and can be appropriately selected depending on the purpose. For example, the convex cylindrical lens, concave cylindrical lens, spherical lens focal length change, lens installation position change, apparatus and heat Examples thereof include a change in the distance between the workpieces of the reversible recording medium and a combination thereof.
In the present invention, the long axis length of the line beam after adjustment is preferably 10 mm to 300 mm, and more preferably 30 mm to 160 mm. Since the erasable area is determined by the length of the long axis of the line beam, if the beam width is narrow, the erasing area becomes narrow. If the beam width is wide, energy is also applied to the erasing unnecessary area, causing energy loss and damage.
The long-axis length of the beam is preferably at least twice as long as the long-axis length of the light emitting portion of the semiconductor laser array, and more preferably at least three times longer. If the long axis length of the beam is shorter than the long axis length of the light emitting portion of the semiconductor laser array, it is necessary to lengthen the light source of the semiconductor laser array in order to secure a long erasing region, and the cost and size of the apparatus are reduced. May grow.
In addition, the minor axis length of the line beam after adjustment is preferably 0.1 mm to 10 mm, and more preferably 0.2 mm to 5 mm. The beam short axis length can control the time for heating the thermoreversible recording medium. If the beam short axis length is narrow, the heating time is short and the erasability is deteriorated. If the beam short axis length is wide, the heating time is short. It becomes longer, and extra energy is added to the thermoreversible recording medium, which requires high energy and cannot be erased at high speed. It is necessary for the apparatus to adjust the beam minor axis length suitable for the erasing characteristics of the thermoreversible recording medium.

  There is no restriction | limiting in particular as an output of the linear beam adjusted in this way, Although it can select suitably according to the objective, 10 W or more are preferable, 20 W or more are more preferable, and 40 W or more are still more preferable. If the output of the laser beam is less than 10 W, it takes a long time to erase the image. If an attempt is made to shorten the image erasing time, the output is insufficient and an image erasing defect occurs. Moreover, there is no restriction | limiting in particular as an upper limit of the output of the said laser beam, Although it can select suitably according to the objective, 500 W or less is preferable, 200 W or less is more preferable, and 120 W or less is still more preferable. If the output of the laser beam exceeds 500 W, the cooling device for the light source of the semiconductor laser may be increased in size.

<Scanning step and scanning means>
The scanning step is a step of scanning, on the thermoreversible recording medium, a linear beam having a uniform light distribution in the long axis length direction in a uniaxial direction that is longer than the long axis length of the light emitting portion of the semiconductor laser array. And can be implemented by scanning means.
The scanning means is not particularly limited as long as it can scan a linear beam in a uniaxial direction, and can be appropriately selected according to the purpose. Examples thereof include a uniaxial galvanometer mirror, a polygon mirror, and a stepping motor mirror. .
The single axis galvanometer mirror or stepping motor mirror can finely control the speed adjustment, the stepping motor mirror is less expensive than the single axis galvanometer mirror, and the polygon mirror is difficult to adjust the speed. Is a low price.

  The scanning speed of the line beam is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 2 mm / s or more, more preferably 10 mm / s or more, and further preferably 20 mm / s or more. If the scanning speed is less than 2 mm / s, it takes time to erase the image. Moreover, there is no restriction | limiting in particular as an upper limit of the scanning speed of the said laser beam, Although it can select suitably according to the objective, 1000 mm / s or less is preferable, 300 mm / s or less is more preferable, 100 mm / s or less is preferable. Further preferred. If the scanning speed exceeds 1000 mm / s, uniform image erasure may be difficult.

Further, the thermoreversible recording medium is moved by a moving means with respect to a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the major axis length direction. It is preferable to erase the image recorded on the thermoreversible recording medium by scanning the line beam on the medium. Examples of the moving means include a conveyor and a stage. In this case, it is preferable that the thermoreversible recording medium is attached to the surface of the container, and the thermoreversible recording medium is moved by moving the container by a conveyor.
Examples of the container include cardboard, a plastic container, and a box.

<Other processes and other means>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably, For example, a control process etc. are mentioned.
The control step is a step of controlling each of the steps, and can be suitably performed by a control unit.
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as a sequencer and a computer.

<Thermal reversible recording medium>
The thermoreversible recording medium is one in which either transparency or color tone reversibly changes depending on temperature.
The thermoreversible recording medium is not particularly limited and may be appropriately selected depending on the purpose. For example, the support, the first thermoreversible recording layer, the photothermal conversion layer, the first, The first oxygen barrier layer, the second oxygen barrier layer, the ultraviolet absorbing layer, the back layer, the protective layer, and the intermediate layer, which are appropriately selected as necessary. And other layers such as an under layer, an adhesive layer, an adhesive layer, a colored layer, an air layer, and a light reflecting layer. By adding a photothermal conversion material to the thermoreversible recording layer, the photothermal conversion layer can be omitted and the first and second thermoreversible recording layers can be combined into one. Each of these layers may have a single layer structure or a laminated structure. However, in the layer provided on the photothermal conversion layer, it is preferable to form the layer using a material that absorbs less at the specific wavelength in order to reduce the energy loss of the laser beam with the specific wavelength to be irradiated.

Here, as shown in FIG. 4A, the layer configuration of the thermoreversible recording medium 100 includes a support 101, a first thermoreversible recording layer 102, a photothermal conversion layer 103, and a second layer on the support. The thermoreversible recording layer 104 may be provided in this order.
Also, as shown in FIG. 4B, the support 101, and the first oxygen barrier layer 105, the first thermoreversible recording layer 102, the photothermal conversion layer 103, and the second thermoreversible recording on the support. There is an embodiment in which the layer 104 and the second oxygen barrier layer 106 are provided in this order.
Further, as shown in FIG. 4C, the support 101, and the first oxygen barrier layer 105, the first thermoreversible recording layer 102, the photothermal conversion layer 103, and the second thermoreversible recording are provided on the support. A mode in which the layer 104, the ultraviolet absorption layer 107, and the second oxygen barrier layer 106 are provided in this order, and the back layer 108 is provided on the surface of the support 101 that does not have the thermoreversible recording layer or the like. There is.
Although not shown, on the second thermoreversible recording layer 104 in FIG. 4A, on the second oxygen barrier layer 106 in FIG. 4B, and on the outermost layer on the second oxygen barrier layer 106 in FIG. 4C. A protective layer may be formed.

-Support-
The support is not particularly limited in its shape, structure, size and the like, and can be appropriately selected according to the purpose. Examples of the shape include a flat plate shape, May have a single-layer structure or a laminated structure, and the size may be appropriately selected according to the size of the thermoreversible recording medium.
Examples of the material for the support include inorganic materials and organic materials.

Examples of the inorganic material include glass, quartz, silicon, silicon oxide, aluminum oxide, SiO ₂ and metal.
Examples of the organic material include paper, cellulose derivatives such as cellulose triacetate, synthetic paper, polyethylene terephthalate, polycarbonate, polystyrene, polymethyl methacrylate, and the like.
The said inorganic material and the said organic material may be used individually by 1 type, and may use 2 or more types together. Among these, organic materials are preferable, films of polyethylene terephthalate, polycarbonate, polymethyl methacrylate, and the like are preferable, and polyethylene terephthalate is particularly preferable.

For the purpose of improving the adhesion of the coating layer, the support is subjected to surface modification by performing corona discharge treatment, oxidation reaction treatment (chromic acid, etc.), etching treatment, easy adhesion treatment, antistatic treatment, etc. Is preferred.
It is preferable to make the support white by adding a white pigment such as titanium oxide to the support.
There is no restriction | limiting in particular as thickness of the said support body, Although it can select suitably according to the objective, 10 micrometers-2,000 micrometers are preferable, and 50 micrometers-1,000 micrometers are more preferable.

-First thermoreversible recording layer and second thermoreversible recording layer-
Each of the first thermoreversible recording layer and the second thermoreversible recording layer (hereinafter sometimes referred to as “thermoreversible recording layer”) is a leuco dye that is an electron donating color-forming compound, and an electron accepting property. It is a thermoreversible recording layer that contains a developer that is a compound and changes the color tone reversibly with heat, and comprises a binder resin and, if necessary, other components.
The leuco dye, which is an electron-donating color-changing compound whose color tone changes reversibly with heat, and the reversible developer, which is an electron-accepting compound, exhibit a phenomenon that causes a visible change reversibly due to temperature changes. It is a possible material and can be changed into a relatively colored state and a decolored state depending on the difference in heating temperature and cooling rate after heating.

--Leuco dye--
The leuco dye is itself a colorless or light dye precursor. The leuco dye is not particularly limited and may be appropriately selected from known ones. Preferable examples include leuco compounds such as phthalocyanine, indophthalyl, spiropyran, azaphthalide, chromenopyrazole, methine, rhodamine anilinolactam, rhodamine lactam, quinazoline, diazaxanthene, and bislactone. Among these, a fluoran-based or phthalide-based leuco dye is particularly preferable in terms of excellent color development / decoloring properties, color, storage stability, and the like. These may be used individually by 1 type, may use 2 or more types together, and can also respond | correspond to multi-color and full color by laminating | stacking the layer which color-emits a different color tone.

--Reversible developer--
The reversible developer is not particularly limited as long as it can reversibly develop and decolorize by using heat as a factor, and can be appropriately selected according to the purpose. For example, (1) A structure having a color developing ability for developing the leuco dye (for example, phenolic hydroxyl group, carboxylic acid group, phosphoric acid group, etc.), and (2) a structure for controlling cohesion between molecules (for example, long-chain hydrocarbon) Preferred examples include compounds having one or more structures selected from the group wherein the groups are linked to each other in the molecule. The linking moiety may be connected to a divalent or higher valent linking group containing a heteroatom, and the long-chain hydrocarbon group also contains at least one of the same linking group and aromatic group. May be.
Phenol is particularly preferred as the structure having the ability to develop (1) the color of the leuco dye.
The (2) structure for controlling the cohesive force between molecules is preferably a long chain hydrocarbon group having 8 or more carbon atoms, more preferably 11 or more, and the upper limit of the carbon number is 40 or less. Preferably, 30 or less is more preferable.

Among the reversible developers, a phenol compound represented by the following general formula (1) is preferable, and a phenol compound represented by the following general formula (2) is more preferable.
In the general formula (1) and (2), ^{R 1} represents an aliphatic hydrocarbon group of a single bond or a 1 to 24 carbon atoms. R ² represents an aliphatic hydrocarbon group having 2 or more carbon atoms which may have a substituent, and the number of carbon atoms is preferably 5 or more, and more preferably 10 or more. R ³ represents an aliphatic hydrocarbon group of 1 to 35 carbon atoms, and carbon number, preferably 6 to 35, 8 to 35 is more preferable. These aliphatic hydrocarbon groups may be used alone or in combination of two or more.

The sum of the carbon numbers of R ¹ , R ² , and R ³ is not particularly limited and may be appropriately selected depending on the purpose. However, the lower limit is preferably 8 or more, more preferably 11 or more. Preferably, the upper limit is preferably 40 or less, and more preferably 35 or less.
If the sum of the carbon numbers is less than 8, the color development stability and decoloring property may be lowered.
The aliphatic hydrocarbon group may be linear or branched, and may have an unsaturated bond, but is preferably linear. In addition, examples of the substituent bonded to the hydrocarbon group include a hydroxyl group, a halogen atom, and an alkoxy group.
X and Y may be the same or different and each represents a divalent group containing an N atom or an O atom. Specific examples include an oxygen atom, an amide group, a urea group, and a diacylhydrazine. Group, oxalic acid diamide group, acylurea group and the like. Among these, an amide group and a urea group are preferable.
n shows the integer of 0-1.

The electron accepting compound (developer) is used in the process of forming a decolored state by using a compound having at least one —NHCO— group or —OCONH— group in the molecule as a decoloring accelerator. This is preferable because an intermolecular interaction is induced between the color accelerator and the developer, and the color development and decoloring characteristics are improved.
There is no restriction | limiting in particular as said decoloring promoter, According to the objective, it can select suitably.
In the thermoreversible recording layer, a binder resin and, if necessary, various additives for improving and controlling the coating characteristics and color developing / decoloring characteristics of the thermoreversible recording layer can be used. Examples of these additives include surfactants, conductive agents, fillers, antioxidants, light stabilizers, color stabilizers, and decolorization accelerators.

--Binder resin--
The binder resin is not particularly limited as long as the thermoreversible recording layer can be bound on the support, and can be appropriately selected according to the purpose. One or two of the conventionally known resins can be selected. A mixture of seeds or more can be used. Among these, in order to improve durability at the time of repetition, a resin curable by heat, ultraviolet rays, electron beams, or the like is preferably used, and a thermosetting resin using an isocyanate compound or the like as a crosslinking agent is particularly preferable. . Examples of the thermosetting resin include a resin having a group that reacts with a crosslinking agent such as a hydroxyl group or a carboxyl group, or a resin obtained by copolymerizing a monomer having a hydroxyl group, a carboxyl group, or the like with another monomer. Examples of such thermosetting resin include phenoxy resin, polyvinyl butyral resin, cellulose acetate propionate resin, cellulose acetate butyrate resin, acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, and the like. Among these, acrylic polyol resin, polyester polyol resin, and polyurethane polyol resin are particularly preferable.
The mixing ratio (mass ratio) of the color former and binder resin in the thermoreversible recording layer is preferably 0.1 to 10 with respect to the color former 1. If the amount of the binder resin is too small, the heat strength of the thermoreversible recording layer may be insufficient. On the other hand, if the amount of the binder resin is too large, the color density may be lowered, causing a problem.

There is no restriction | limiting in particular as said crosslinking agent, According to the objective, it can select suitably, For example, isocyanate, amino resin, a phenol resin, amines, an epoxy compound, etc. are mentioned. Among these, isocyanates are preferable, and polyisocyanate compounds having a plurality of isocyanate groups are particularly preferable.
The amount of the crosslinking agent added to the binder resin is not particularly limited, but the ratio of the functional group of the crosslinking agent to the number of active groups contained in the binder resin is preferably 0.01-2. Below this, the heat strength is insufficient, and when added more than this, the coloring and decoloring properties are adversely affected.
Furthermore, you may use the catalyst used for this kind of reaction as a crosslinking accelerator.

  There is no restriction | limiting in particular as a gel fraction of the thermosetting resin at the time of the said thermal crosslinking, 30% or more is preferable, 50% or more is more preferable, and 70% or more is especially preferable. When the gel fraction is less than 30%, the crosslinked state is not sufficient and the durability may be inferior.

  As a method for distinguishing whether the binder resin is in a crosslinked state or in a non-crosslinked state, for example, it can be distinguished by immersing the coating film in a highly soluble solvent. That is, the binder resin in the non-crosslinked state is dissolved in the solvent and does not remain in the solute.

The other components in the thermoreversible recording layer are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include surfactants and plasticizers from the viewpoint of facilitating image recording. .
Known methods can be used as the solvent, the coating liquid dispersing device, the coating method, the drying / curing method, and the like used in the thermoreversible recording layer coating solution.
In the thermoreversible recording layer coating solution, each material may be dispersed in a solvent using the dispersing device, or may be dispersed and mixed in a solvent alone. Further, it may be dissolved by heating and precipitated by rapid cooling or slow cooling.

  The method for forming the thermoreversible recording layer is not particularly limited and may be appropriately selected depending on the purpose. For example, (1) the resin, the leuco dye, and the reversible developer are contained in a solvent. A method of applying a dissolved or dispersed coating solution for a thermoreversible recording layer on a support and cross-linking it at the same time or after evaporating the solvent to form a sheet or the like, (2) dissolving only the resin A method in which a coating solution for a thermoreversible recording layer in which the leuco dye and the reversible developer are dispersed in a solvent is coated on a support, and the solvent is evaporated to form a sheet or the like, or at the same time or thereafter, 3) A method in which the resin, the leuco dye, and the reversible developer are heated and melted and mixed with each other without using a solvent, and the molten mixture is molded into a sheet or the like and cooled and then cross-linked is preferable. It is mentioned in. In these, a sheet-like thermoreversible recording medium can be formed without using the support.

The solvent used in the above (1) or (2) varies depending on the kind of the resin, the leuco dye, and the reversible developer, and cannot be defined unconditionally. For example, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone , Chloroform, carbon tetrachloride, ethanol, toluene, benzene and the like.
The reversible developer is dispersed in the form of particles in the thermoreversible recording layer.
In the coating liquid for the thermoreversible recording layer, various pigments, antifoaming agents, pigments, dispersants, slip agents, preservatives, crosslinking agents, plasticizers, etc. are used for the purpose of expressing high performance as a coating material. It may be added.

The method for coating the thermoreversible recording layer is not particularly limited and may be appropriately selected depending on the intended purpose. The support may be conveyed continuously in a roll or cut into a sheet. On top, for example, blade coating, wire bar coating, spray coating, air knife coating, bead coating, curtain coating, gravure coating, kiss coating, reverse roll coating, dip coating, die coating Etc. are applied by a known method.
The drying conditions for the thermoreversible recording layer coating liquid are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include room temperature to 140 ° C. for about 10 seconds to 10 minutes. It is done.
There is no restriction | limiting in particular in the thickness of the said thermoreversible recording layer, According to the objective, it can select suitably, For example, 1 micrometer-20 micrometers are preferable, and 3 micrometers-15 micrometers are more preferable. If the thickness of the thermoreversible recording layer is too thin, the color density may be low and the contrast of the image may be low. On the other hand, if the thickness is too thick, the heat distribution in the layer will be large and the color will not reach the color development temperature. May occur, making it impossible to obtain a desired color density.
In addition, it is also possible to add a photothermal conversion material to the thermoreversible recording layer, in which case the photothermal conversion layer and the barrier layer can be omitted, and the first and second thermoreversible recording layers are combined into one. Is also possible.

-Photothermal conversion layer-
The photothermal conversion layer contains at least a photothermal conversion material having a role of absorbing the laser beam with high efficiency and generating heat. In addition, a barrier layer may be formed between the thermoreversible recording layer and the photothermal conversion layer for the purpose of suppressing the interaction, and a layer having good thermal conductivity is preferred as the material. The layer sandwiched between the thermoreversible recording layer and the photothermal conversion layer can be appropriately selected according to the purpose, and is not limited thereto.
The photothermal conversion material can be roughly classified into an inorganic material and an organic material.

Examples of the inorganic material include carbon black, metals such as carbon black, Ge, Bi, In, Te, Se, and Cr, and alloys containing them, lanthanum boride, tungsten oxide, ATO, ITO, and the like. These are formed in layers by bonding a vacuum deposition method or a particulate material with a resin or the like.
As the organic material, various dyes can be appropriately used according to the light wavelength to be absorbed. However, when a semiconductor laser is used as the light source, the organic material has an absorption peak in a wavelength range of 700 nm to 1,500 nm. Near infrared absorbing dyes are used. Specific examples include cyanine dyes, quinone dyes, quinoline derivatives of indonaphthol, phenylenediamine nickel complexes, and phthalocyanine compounds. In order to perform repeated image processing, it is preferable to select a photothermal conversion material having excellent heat resistance, and phthalocyanine compounds are particularly preferable in this respect.
The near infrared absorbing dyes may be used alone or in combination of two or more.

When the photothermal conversion layer is provided, the photothermal conversion material is usually used in combination with a resin. The resin used for the light-to-heat conversion layer is not particularly limited and can be appropriately selected from known ones that can hold the inorganic material and the organic material. A curable resin or the like is preferable, and the same binder resin as that used in the recording layer can be suitably used. Among these, in order to improve durability at the time of repetition, a resin that can be cured by heat, ultraviolet rays, electron beams, or the like is preferably used, and a thermal crosslinking resin using an isocyanate compound or the like as a crosslinking agent is particularly preferable. In the binder resin, the hydroxyl value is preferably 50 mgKOH / g to 400 mgKOH / g.
There is no restriction | limiting in particular in the thickness of the said photothermal conversion layer, According to the objective, it can select suitably, It is preferable that they are 0.1 micrometer-20 micrometers.

-First oxygen barrier layer and second oxygen barrier layer-
As the first oxygen barrier layer and the second oxygen barrier layer (hereinafter sometimes simply referred to as an oxygen barrier layer), the first thermoreversible layer is formed by preventing oxygen from entering the thermoreversible recording layer. In order to prevent photodegradation of the leuco dye in the recording layer and the second thermoreversible recording layer, it is preferable to provide oxygen barrier layers above and below the first thermoreversible recording layer and the second thermoreversible recording layer. That is, it is preferable to provide a first oxygen barrier layer between the support and the first thermoreversible recording layer, and to provide a second oxygen barrier layer on the second thermoreversible recording layer.

The material for forming the first oxygen barrier layer and the second oxygen barrier layer is not particularly limited and may be appropriately selected depending on the purpose. The resin has a large visible part transmittance and a low oxygen permeability. Or a polymer film etc. are mentioned. The oxygen barrier layer is selected depending on its use, oxygen permeability, transparency, ease of coating, adhesion, and the like.
Specific examples of the oxygen barrier layer include polyacrylic acid alkyl ester, polymethacrylic acid alkyl ester, polymethacrylonitrile, polyalkyl vinyl ester, polyalkyl vinyl ether, polyfluorinated vinyl, polystyrene, vinyl acetate copolymer, acetic acid. Cellulose, polyvinyl alcohol, polyvinylidene chloride, acetonitrile copolymer, vinylidene chloride copolymer, poly (chlorotrifluoroethylene), ethylene-vinyl alcohol copolymer, polyacrylonitrile, acrylonitrile copolymer, polyethylene terephthalate, nylon-6 And silica deposited film, alumina deposited film, silica / aluminum with inorganic oxide deposited on a polymer film such as polyethylene terephthalate or nylon. Such as vapor deposition film, and the like. Among these, a film obtained by depositing an inorganic oxide on a polymer film is preferable.

The oxygen permeability of the oxygen barrier layer is not particularly limited, but is preferably 20 ml / m ² / day / MPa or less, more preferably 5 ml / m ² / day / MPa or less, and 1 ml / m ² / day / MPa. The following are particularly preferred: If the oxygen permeability exceeds 20 ml / m ² / day / MPa, photodegradation of the leuco dye in the first thermoreversible recording layer and the second thermoreversible recording layer may not be suppressed.
The oxygen permeability can be measured, for example, by a measuring method according to JIS K7126 B method.
The oxygen barrier layer may be provided such that the thermoreversible recording layer is sandwiched between the oxygen barrier layers, such as the lower side of the thermoreversible recording layer or the back surface of the support. Thereby, oxygen penetration into the thermoreversible recording layer can be more effectively prevented, and the photodegradation of the leuco dye can be further reduced.

A method for forming the first oxygen barrier layer and the second oxygen barrier layer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a melt extrusion method, a coating method, and a laminating method. .
The thicknesses of the first oxygen barrier layer and the second oxygen barrier layer vary depending on the oxygen permeability of the resin or polymer film, but are preferably 0.1 μm to 100 μm. If it is thinner than this, the oxygen barrier is incomplete, and if it is thicker, the transparency is lowered.
An adhesive layer may be provided between the oxygen barrier layer and the lower layer. The method for forming the adhesive layer is not particularly limited, and examples thereof include ordinary coating methods and laminating methods. The thickness of the adhesive layer is not particularly limited, but is preferably 0.1 μm to 5 μm. The adhesive layer may be cured with a crosslinking agent. The same materials as those used in the thermoreversible recording layer can be preferably used.

-Protective layer-
In the thermoreversible recording medium of the present invention, a protective layer is preferably provided on the thermoreversible recording layer for the purpose of protecting the thermoreversible recording layer. There is no restriction | limiting in particular in this protective layer, According to the objective, it can select suitably, For example, you may form in one or more layers, and it is preferable to provide in the outermost surface exposed.
The protective layer contains a binder resin and, if necessary, other components such as a filler, a lubricant and a color pigment.
The binder resin for the protective layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a thermosetting resin, an ultraviolet (UV) curable resin, an electron beam curable resin, and the like are preferable. Among these, ultraviolet (UV) curable resins and thermosetting resins are particularly preferable.
The UV curable resin can form a very hard film after curing, and can suppress damage due to physical contact with the surface and deformation of the medium due to laser heating, so thermoreversible recording with excellent repeated durability A medium is obtained.
Moreover, although the said thermosetting resin is a little inferior to the said UV curable resin, it can make the surface hard similarly and is excellent in repeated durability.

  There is no restriction | limiting in particular as said UV curable resin, According to the objective, it can select suitably according to the objective, for example, urethane acrylate type, epoxy acrylate type, polyester acrylate type, polyether acrylate type, vinyl type And monomers such as unsaturated polyester oligomers and various monofunctional and polyfunctional acrylates, methacrylates, vinyl esters, ethylene derivatives, and allyl compounds. Among these, tetrafunctional or higher polyfunctional monomers or oligomers are particularly preferable. By mixing two or more of these monomers or oligomers, the hardness, shrinkage, flexibility, coating strength, etc. of the resin film can be appropriately adjusted.

Further, in order to cure the monomer or oligomer using ultraviolet rays, it is necessary to use a photopolymerization initiator and a photopolymerization accelerator.
The addition amount of the photopolymerization initiator or photopolymerization accelerator is not particularly limited, but is preferably 0.1% by mass to 20% by mass, and preferably 1% by mass to 10% by mass with respect to the total mass of the resin component of the protective layer. The mass% is more preferable.

The UV irradiation for curing the UV curable resin can be performed using a known UV irradiation device, and includes, for example, a light source, a lamp, a power source, a cooling device, a transport device, and the like. Is mentioned.
Examples of the light source include a mercury lamp, a metal halide lamp, a potassium lamp, a mercury xenon lamp, and a flash lamp. The wavelength of the light source can be appropriately selected according to the ultraviolet absorption wavelength of the photopolymerization initiator and photopolymerization accelerator added to the thermoreversible recording medium composition.
The conditions for the ultraviolet irradiation are not particularly limited and may be appropriately selected depending on the purpose. For example, the lamp output, the conveyance speed, etc. may be determined according to the irradiation energy necessary for crosslinking the resin. .

  In order to improve transportability, silicone having a polymerizable group, a polymer grafted with silicone; a release agent such as wax and zinc stearate; and a lubricant such as silicone oil can be added. As these addition amounts, 0.01 mass%-50 mass% are preferable with respect to the resin component total mass of a protective layer, and 0.1 mass%-40 mass% are more preferable. These may be used individually by 1 type and may use 2 or more types together. Moreover, it is preferable to use a conductive filler as a countermeasure against static electricity, and it is particularly preferable to use a needle-shaped conductive filler.

Although there is no restriction | limiting in particular as a particle size of the said filler, For example, 0.01 micrometer-10.0 micrometers are preferable, and 0.05 micrometer-8.0 micrometers are more preferable. The addition amount of the filler is preferably 0.001 to 2 parts by mass and more preferably 0.005 to 1 part by mass with respect to 1 part by mass of the resin.
The protective layer may contain conventionally known surfactants, leveling agents, antistatic agents and the like as additives.

Moreover, as the thermosetting resin, for example, the same resin as the binder resin used in the thermoreversible recording layer can be suitably used.
The thermosetting resin is preferably cross-linked. Accordingly, as the thermosetting resin, it is preferable to use a resin having a group that reacts with a curing agent such as a hydroxyl group, an amino group, or a carboxyl group, and a polymer having a hydroxyl group is particularly preferable. In order to improve the strength of the polymer-containing layer having the ultraviolet absorbing structure, a sufficient coating strength can be obtained by using a polymer having a hydroxyl value of 10 mgKOH / g or more, more preferably 30 mgKOH / g or more. More preferably, it is 40 mgKOH / g or more. By providing sufficient coating strength, deterioration of the thermoreversible recording medium can be suppressed even when image recording / erasing is repeated.
There is no restriction | limiting in particular as said hardening | curing agent, For example, the thing similar to the hardening | curing agent used with the said thermoreversible recording layer can be used suitably.

There are no particular limitations on the solvent used in the protective layer coating solution, the dispersion device of the coating solution, the coating method of the protective layer, the drying method, and the like, and known methods used in the recording layer can be used. When an ultraviolet curable resin is used, a curing step by ultraviolet irradiation that is applied and dried is required, but the ultraviolet irradiation device, the light source, and the irradiation conditions are as described above.
The thickness of the protective layer is not particularly limited, but is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 10 μm, and particularly preferably 1.5 μm to 6 μm. When the thickness is less than 0.1 μm, the function as the protective layer of the thermoreversible recording medium cannot be sufficiently achieved, and the deterioration due to the repeated history due to heat is quickly deteriorated, so that it cannot be used repeatedly. If the thickness exceeds 20 μm, it may not be possible to transfer heat sufficient for heat sensitivity in the lower layer of the protective layer, and image recording and erasure due to heat may not be sufficiently performed.

-UV absorbing layer-
The thermoreversible recording medium is preferably provided with an ultraviolet absorbing layer for the purpose of preventing the leuco dye in the thermoreversible recording layer from being colored by ultraviolet rays and preventing disappearance due to photodegradation. Can be improved. It is preferable that the thickness of the ultraviolet absorbing layer is appropriately selected so that the ultraviolet absorbing layer absorbs ultraviolet rays of 390 nm or less.

The ultraviolet absorbing layer contains at least a binder resin and an ultraviolet absorber, and further contains other components such as a filler, a lubricant, and a coloring pigment as necessary.
There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably, Resin components, such as binder resin of the said thermoreversible recording layer, a thermoplastic resin, and a thermosetting resin, can be used. Examples of the resin component include polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide, and the like.

As the ultraviolet absorber, any of organic and inorganic compounds can be used.
Further, it is preferable to use a polymer having an ultraviolet absorbing structure (hereinafter sometimes referred to as “ultraviolet absorbing polymer”).
Here, the polymer having an ultraviolet absorbing structure means a polymer having an ultraviolet absorbing structure (for example, an ultraviolet absorbing group) in the molecule. Examples of the ultraviolet absorbing structure include a salicylate structure, a cyanoacrylate structure, a benzotriazole structure, a benzophenone structure, and the like. Among these, an ultraviolet ray of 340 to 400 nm, which is a cause of photodegradation of a leuco dye, is absorbed. A benzotriazole structure and a benzophenone structure are particularly preferable.
The ultraviolet absorbing polymer is preferably crosslinked. Accordingly, as the ultraviolet absorbing polymer, it is preferable to use a polymer having a group that reacts with a curing agent such as a hydroxyl group, an amino group, or a carboxyl group, and a polymer having a hydroxyl group is particularly preferable. In order to improve the strength of the polymer-containing layer having the ultraviolet absorbing structure, a sufficient coating strength can be obtained by using a polymer having a hydroxyl value of 10 mgKOH / g or more, more preferably 30 mgKOH / g or more. More preferably, it is 40 mgKOH / g or more. By providing a sufficient coating strength, deterioration of the recording medium can be suppressed even if repeated erasure printing is performed.

  Although there is no restriction | limiting in particular as the thickness of the said ultraviolet absorption layer, 0.1 micrometer-30 micrometers are preferable, and 0.5 micrometer-20 micrometers are more preferable. Solvents used in the coating solution for the UV absorbing layer, a dispersion device for the coating solution, a coating method for the UV absorbing layer, a drying / curing method for the UV absorbing layer, etc. are known methods used in the thermoreversible recording layer. Can be used.

-Intermediate layer-
The thermoreversible recording medium is not particularly limited, but the adhesion between the thermoreversible recording layer and the protective layer is improved, the thermoreversible recording layer is prevented from being altered by coating the protective layer, and the additive in the protective layer is thermally reversible. For the purpose of preventing the transfer to the recording layer, it is preferable to provide an intermediate layer between them, whereby the storability of the color image can be improved.

There is no restriction | limiting in particular as said intermediate | middle layer, What contains other components, such as a filler, a lubricant, and a color pigment, is further included as needed at least containing binder resin.
There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably, Resin components, such as binder resin of the said thermoreversible recording layer, a thermoplastic resin, and a thermosetting resin, can be used. Examples of the resin component include polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide, and the like.

The intermediate layer preferably contains an ultraviolet absorber. As the ultraviolet absorber, any of organic and inorganic compounds can be used.
Further, an ultraviolet absorbing polymer may be used, and it may be cured with a crosslinking agent. As these, those similar to those used in the protective layer can be suitably used.
The thickness of the intermediate layer is preferably 0.1 μm to 20 μm, and more preferably 0.5 μm to 5 μm. For the solvent used in the intermediate layer coating solution, the coating liquid dispersing device, the intermediate layer coating method, the intermediate layer drying / curing method, etc., known methods used in the thermoreversible recording layer may be used. it can.

-Under layer-
The thermoreversible recording medium is not particularly limited. However, in order to increase the sensitivity by effectively using the applied heat, or to improve the adhesion between the support and the thermoreversible recording layer, the recording layer material to the support For the purpose of preventing penetration, an under layer may be provided between the thermoreversible recording layer and the support.
Examples of the under layer include those containing at least hollow particles, a binder resin, and further containing other components as required.

Examples of the hollow particles include single hollow particles in which one hollow portion is present in the particles, and multi-hollow particles in which many hollow portions are present in the particles. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular as a material of the said hollow particle, Although it can select suitably according to the objective, For example, a thermoplastic resin etc. are mentioned suitably. The hollow particles may be appropriately manufactured or commercially available. Examples of the commercially available products include Microsphere R-300 (manufactured by Matsumoto Yushi Co., Ltd.); Ropaque HP1055, Ropaque HP433J (both manufactured by Nippon Zeon Co., Ltd.); and SX866 (manufactured by JSR Corporation).
There is no restriction | limiting in particular in the addition amount in the said under layer of the said hollow particle, According to the objective, it can select suitably, For example, 10 mass%-80 mass% are preferable.
As the binder resin, the same resin as the thermoreversible recording layer or the layer containing the polymer having the ultraviolet absorption structure can be used.
The under layer may contain at least one of inorganic fillers such as calcium carbonate, magnesium carbonate, titanium oxide, silicon oxide, aluminum hydroxide, kaolin, and talc, and various organic fillers.
In addition, the under layer may further contain a lubricant, a surfactant, a dispersant, and the like.
There is no restriction | limiting in particular as thickness of the said under layer, According to the objective, it can select suitably, 0.1 micrometer-50 micrometers are preferable, 2 micrometers-30 micrometers are more preferable, and 12 micrometers-24 micrometers are especially preferable.

-Back layer-
The thermoreversible recording medium is not particularly limited, and a back layer may be provided on the side of the support opposite to the surface on which the thermoreversible recording layer is provided in order to improve curling and antistatic properties and transportability.
There is no restriction | limiting in particular as said back layer, What contains other components, such as a filler, an electroconductive filler, a lubricant, and a color pigment, further contains a binder resin at least.

There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably, For example, a thermosetting resin, an ultraviolet-ray (UV) curable resin, an electron beam curable resin, etc. are mentioned, These Among these, ultraviolet (UV) curable resins and thermosetting resins are particularly preferable.
As the ultraviolet curable resin, the thermosetting resin, the filler, the conductive filler, and the lubricant, the same materials as those used in the thermoreversible recording layer or the protective layer are preferably used. it can.

-Adhesive layer and adhesive layer-
The thermoreversible recording medium can be obtained in the form of a thermoreversible recording label by providing an adhesive layer or an adhesive layer on the opposite surface of the support to the recording layer forming surface.
There is no restriction | limiting in particular as a material of the said contact bonding layer and the said adhesion layer, According to the objective, it can select suitably from what is generally used.

The material of the adhesive layer and the adhesive layer may be a hot melt type. Moreover, a release paper may be used and a non-release paper type may be used. By providing the adhesive layer or the pressure-sensitive adhesive layer in this manner, the recording layer can be attached to the entire surface or a part of a thick substrate such as a magnetic stripe-added PVC card that is difficult to apply the recording layer. This improves the convenience of the thermoreversible recording medium, such as being able to display part of the information stored in the magnetism.
A thermoreversible recording label provided with such an adhesive layer or adhesive layer is also suitable for thick cards such as IC cards and optical cards.

-Colored layer-
The thermoreversible recording medium may be provided with a colored layer between the support and the recording layer for the purpose of improving visibility.
The colored layer can be formed by applying a solution or dispersion containing a colorant and a resin binder to a target surface and drying, or simply bonding a colored sheet.

The colored layer can be a color print layer.
Examples of the colorant in the color printing layer include various dyes and pigments contained in color inks used in conventional full color printing.
Examples of the resin binder include various thermoplastic resins, thermosetting resins, ultraviolet curable resins, and electron beam curable resins.
There is no restriction | limiting in particular as thickness of the said color printing layer, Since it changes suitably with respect to printing color density, it can select according to desired printing color density.

The thermoreversible recording medium may be used in combination with an irreversible recording layer. In this case, the color tone of each recording layer may be the same or different.
In addition, a part of the same surface as the recording layer of the thermoreversible recording medium, a part of the entire surface, or a part of the opposite surface may be printed with offset printing, gravure printing, or an arbitrary pattern by an inkjet printer, a thermal transfer printer, a sublimation printer, or the like. In addition, an OP varnish layer mainly composed of a curable resin may be provided on a part or the entire surface of the colored layer.
Examples of the pattern include characters, patterns, patterns, photographs, information detected by infrared rays, and the like.
It is also possible to add a dye or pigment to any one of the simply configured layers for coloring.
Further, the thermoreversible recording medium can be provided with a hologram for security. In addition, in order to impart design properties, it is possible to provide a relief image, an intaglio shape, or a design such as a person image, a company emblem, or a symbol mark.

-Shape and application of thermoreversible recording medium-
The thermoreversible recording medium can be processed into a desired shape according to the application, for example, a card shape, a tag shape, a label shape, a sheet shape, a roll shape, or the like.
Moreover, what was processed into the card form can be applied to a prepaid card, a point card, and further a credit card.
Furthermore, a tag-shaped size smaller than the card size can be used for a price tag or the like, and a tag-shaped size larger than the card size can be used for process management, a shipping instruction, a ticket, or the like.
Since the label can be affixed, it is processed into various sizes and can be affixed to carts, containers, boxes, containers, etc. that are repeatedly used and used for process management, article management, and the like. In addition, since the recording range is wide at a sheet size larger than the card size, it can be used for general documents, process management instructions, and the like.

-Example of combination with thermoreversible recording member RF-ID-
The thermoreversible recording member includes the reversible thermosensitive recording layer (recording layer) capable of reversible display and an information storage unit (integrated) on the same card or tag, and stores information stored in the information storage unit. By displaying the portion on the recording layer, information can be confirmed by simply looking at the card or tag without a special device, which is excellent in convenience. Further, when the contents of the information storage unit are rewritten, the thermoreversible recording medium can be used repeatedly many times by rewriting the display of the thermoreversible recording unit.
The information storage unit is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a magnetic recording layer, a magnetic stripe, an IC memory, an optical memory, and an RF-ID tag. . When used for process management, article management, etc., an RF-ID tag can be particularly preferably used.
The RF-ID tag includes an IC chip and an antenna connected to the IC chip.

The thermoreversible recording member includes the reversible displayable recording layer and an information storage unit. A suitable example of the information storage unit is an RF-ID tag.
FIG. 11 shows an example of a schematic diagram of an RF-ID tag. The RF-ID tag 85 includes an IC chip 81 and an antenna 82 connected to the IC chip 81. The IC chip 81 is divided into four parts: a storage unit, a power supply adjustment unit, a transmission unit, and a reception unit, and each performs communication by sharing the function. In the communication, the RF-ID tag 85 and the antenna of the reader / writer communicate with each other by radio waves to exchange data. Specifically, there are two types, an electromagnetic induction method in which an RF-ID85 antenna receives a radio wave from a reader / writer and generates electromotive force by electromagnetic induction by a resonance action and a radio wave method activated by a radiated electromagnetic field. In both cases, the IC chip 81 in the RF-ID tag 85 is activated by an external electromagnetic field, converts the information in the chip into a signal, and then transmits a signal from the RF-ID tag 85. This information is received by the antenna on the reader / writer side and recognized by the data processing device, and data processing is performed on the software side.

The RF-ID tag is processed into a label shape or a card shape, and the RF-ID tag can be attached to the thermoreversible recording medium. The RF-ID tag can be attached to the recording layer surface or the back layer surface, but is preferably attached to the back layer surface.
In order to bond the RF-ID tag and the thermoreversible recording medium, a known adhesive or pressure-sensitive adhesive can be used.
The thermoreversible recording medium and the RF-ID tag may be integrated into a card shape or tag shape by laminating or the like.

An example of how to use the thermoreversible recording member in combination with the thermoreversible recording medium and the RF-ID tag in process management will be described.
The process line in which the containers containing the delivered raw materials are transported is equipped with means for writing a visible image in a non-contact manner on the display part while being transported, and means for non-contact erasing, and transmission of electromagnetic waves. Is provided with a reader / writer for reading and rewriting the RF-ID information provided in the container in a non-contact manner. In addition, the process line is provided with a control means for automatically branching, weighing, managing, etc. on the physical distribution line using the individual information read and written without contact while the container is being conveyed. ing.
Information such as the article name and quantity is recorded on the thermoreversible recording medium and the RF-ID tag for the RF-ID thermoreversible recording medium attached to the container, and inspection is performed. In the next step, a processing instruction is given to the delivered raw material, information is recorded on the thermoreversible recording medium and the RF-ID tag, and a processing instruction is made and the processing proceeds. Next, order information is recorded in the thermoreversible recording medium and the RF-ID tag as an ordering instruction for the processed product, the shipping information is read from the container collected after the product is shipped, and the delivery container and the RF are again read. -Used as a thermoreversible recording medium with ID.
At this time, since it is non-contact recording to the thermoreversible recording medium using a laser, information can be erased and recorded without peeling the thermoreversible recording medium from a container or the like. Since information can be recorded in a non-contact manner, the process can be managed in real time, and information in the RF-ID tag can be simultaneously displayed on the thermoreversible recording medium.

<Image recording and erasing mechanism>
The image recording and image erasing mechanism is a mode in which the color tone reversibly changes due to heat. The above aspect comprises a leuco dye and a reversible developer (hereinafter sometimes referred to as “developer”), and the color tone reversibly changes between heat and a colored state by heat.
FIG. 5A shows an example of a temperature-color density change curve of a thermoreversible recording medium having a thermoreversible recording layer containing the leuco dye and the developer in the resin, and FIG. 5B shows a transparent state. And a color development / decoloration mechanism of the thermoreversible recording medium in which the color development state changes reversibly with heat.
First, when gradually heated the recording layer in First decolored state (A), at the melting temperature T _1, and the leuco dye and the color developer are mixed melt, molten color developed state caused color development ( B). When rapidly cooled from the melt color state (B), the color state can be lowered to room temperature, and the color state is stabilized and becomes a fixed color state (C). Whether or not this color development state has been obtained depends on the rate of temperature decrease from the melted state. In slow cooling, the color disappears in the process of temperature decrease, and the same color disappearance state (A) as the initial state or the color development state by rapid cooling ( The density is relatively lower than in C). On the other hand, when gradually raising the temperature again from the colored state (C), the color is erased at a lower temperature T ₂ than the coloring temperature (E from D), when the temperature is lowered from this state, the initial same decolorized state (A Return to).
The colored state (C) obtained by quenching from the molten state is a state in which the leuco dye and the developer are mixed in a state in which molecules can contact each other and form a solid state. There are many cases. In this state, the molten mixture of the leuco dye and the developer (the color mixture) crystallizes and maintains color development, and it is considered that the color development is stabilized by the formation of this structure. On the other hand, the decolored state is a state in which both phases are separated. This state is a state in which molecules of at least one compound aggregate to form a domain or crystallize, and the leuco dye and the developer are separated and stabilized by aggregation or crystallization. It is considered to be a state. In many cases, the color developer is crystallized as a result of phase separation between the two, thereby causing more complete color erasure.
Incidentally, it is shown in Figure 5A, decoloring by slow cooling from the molten state, and aggregate structure also T ₂ both decoloring change after heating from the colored state, the crystallization of the phase separation and the color developer is caused ing.
Further, in FIG. 5A, when the recording layer is repeatedly heated to a temperature T ₃ that is equal to or higher than the melting temperature T _{1, an} erasure defect that cannot be erased even when heated to the erasing temperature may occur. This is presumably because the developer undergoes thermal decomposition and is difficult to aggregate or crystallize and separate from the leuco dye. To suppress the deterioration of the thermoreversible recording medium caused by repeated, by reducing the difference between the melting temperature T ₁ of the said temperature T ₃ in FIG. 5A when heating the thermoreversible recording medium, the heat generated by repeated Deterioration of the reversible recording medium can be suppressed.

Here, an outline of the image erasing apparatus of the present invention will be described with reference to the drawings.
The image erasing apparatus of FIG. 6 has a semiconductor laser (LD) array 1, a width direction parallelizing means 2, a long axis length direction light distribution control means 7, a beam size adjusting means 9, and a scanning means 5. ing.

As the semiconductor laser (LD) array 1, an LD array in which a plurality of LD light sources are arranged is used.
As the width direction parallelizing means 2, an optical lens is used which makes the spread of the beam in the width direction of the laser light emitted from the semiconductor laser array parallel.
The long axis length direction light distribution control means 7 has a function of making the long axis length of the line beam longer than the long axis length of the light emitting portion of the semiconductor laser array and making the light distribution uniform in the long axis length direction. is doing.
As the beam size adjusting means 9, an optical system lens capable of adjusting at least one of the major axis length and the minor axis length of the line beam is used.

As the scanning means 5, (1) laser light scanning by a uniaxial galvanometer mirror can perform fine scanning control, but the cost becomes high. (2) Laser scanning by a stepping motor mirror can perform fine scanning control, and the cost is lower than that of a galvanometer mirror. (3) Laser light scanning with a polygon mirror can only perform scanning control at a constant speed, but is low in cost.
Further, the thermoreversible recording medium can be moved without providing the scanning means. As an implementation method, (1) the thermoreversible recording medium is moved on the stage, (2) the thermoreversible recording medium (the medium is attached to the box and the box is moved by the conveyor) is moved by the conveyor.

FIG. 7 is a schematic view showing a specific embodiment of the image erasing apparatus of the present invention.
The image erasing apparatus of FIG. 7 uses an LD array in which 19 LD light sources are arranged, and the major axis length of the light emitting portions of the first to 19th semiconductor laser arrays is 10 mm.
The laser beam emitted from the semiconductor laser array 1 is converted into parallel light in the width direction by the cylindrical lens 2 as the width direction parallelizing means, and the two spherical lenses 4 and 6 are used in the width direction and the major axis length. The direction is expanded uniformly, and the width is adjusted by the cylindrical lenses 3 and 8.
In order to make the light distribution in the long axis length direction uniform, the lens 15 having a function of spreading the laser light from the spherical lens 6 to make it uniform and widen the width (for example, a concave or convex lens array, a Fresnel lens) In this embodiment, a convex lens array and a Fresnel lens are used.
Since the light distribution of the line-shaped beam emitted from the width direction parallelizing means 2 is a combination of the light emitted from a plurality of light sources, an optical system for equalizing is required instead of being uniform. It is necessary to form.
Specifically, a single-sided convex lens with a focal length of 70 mm is used for the spherical lens 6, a single-sided convex lens with a focal length of 200 mm is used for the spherical lens 4, and a single-sided convex lens with a focal length of 200 mm is used for the cylindrical lens 8. By using a cylindrical lens 3 with a single-sided concave lens having different focal lengths (for example, -1,000 mm, -400 mm, -200 mm) according to the beam width, the beam width of the embodiment can be realized. The convex lens array has a period of 400 μm and has a step in the length direction.

  According to the image erasing apparatus shown in FIGS. 6 and 7, as shown in FIG. 8, the obtained line beam has a uniform light distribution in the major axis length direction, and the major axis length of the line beam. Is one side of the erased area. The length (distance) for scanning the line beam is the remaining side of the erased area. The laser beam scanning method can be performed only in one axial direction.

According to the image erasing apparatus and the image erasing method of the present invention, the following effects can be obtained.
(1) In erasing with a line beam, it is only necessary to scan the laser beam in only one direction, the number of scanning mirrors can be reduced, control is facilitated, and cost can be reduced.
(2) Erasing with a line beam enables erasing with lower energy than a circular beam. This is due to the fact that energy loss due to thermal diffusion can be reduced by using a line beam light source.
(3) Since it is not necessary to perform a jump (laser beam scanning without irradiating a laser beam) with a laser beam scan, the erasing time does not increase due to the jump.
(4) Compared with the fiber coupled LD, the LD array light source can easily obtain a high output at a low price.
(5) When repeated erasing is performed, the density of the normal background increases, but the limit of 0.02 increase with respect to the initial background density is 400 times for the circular beam and 5,000 times for the line beam. And has been greatly improved. This is because there is no need to overlap laser beam scanning.

The image erasing method and the image erasing apparatus of the present invention can be repeatedly erased in a non-contact manner on a thermoreversible recording medium such as a label affixed to a container such as a cardboard or a plastic container. For this reason, it can be used particularly suitably for a physical distribution system. In this case, for example, an image can be formed and erased on the label while moving the cardboard or plastic container placed on a belt conveyor, and it is not necessary to stop the line, thereby reducing the shipping time. it can.
Further, the cardboard or the plastic container to which the label is attached can be reused as it is without peeling off the label, and the image can be erased and formed again.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Production Example 1)
<Manufacture of thermoreversible recording medium>
A thermoreversible recording medium in which the color tone reversibly changes due to heat was produced as follows.

-Support-
As a support, a 125 μm thick white turbid polyester film (manufactured by Teijin DuPont Co., Ltd., Tetron film U2L98W) was used.

-Formation of first oxygen barrier layer-
Add 5 parts by mass of urethane adhesive (TM-567 manufactured by Toyo Morton Co., Ltd.), 0.5 parts by mass of isocyanate (CAT-RT-37 manufactured by Toyo Morton Co., Ltd.), and 5 parts by mass of ethyl acetate, and stir well. Thus, an oxygen barrier layer coating solution was prepared.
Next, the oxygen barrier layer coating solution was applied with a wire bar onto a silica-deposited PET film (Mitsubishi Resin, Tech Barrier HX, oxygen permeability: 0.5 ml / m ² / day / MPa). And heated at 80 ° C. for 1 minute and dried. This silica-deposited PET film with an oxygen barrier layer was bonded onto the support and heated at 50 ° C. for 24 hours to form a first oxygen barrier layer having a thickness of 12 μm.

-Formation of first thermoreversible recording layer-
5 parts by mass of a reversible developer represented by the following structural formula (1), and 0.5 parts by mass of two types of decoloring accelerators represented by the following structural formulas (2) and (3) 10 parts by mass of a polyol 50% by mass solution (hydroxyl value = 200 mg KOH / g) and 80 parts by mass of methyl ethyl ketone were pulverized and dispersed using a ball mill until the average particle size was about 1 μm.

Next, 1 part by mass of 2-anilino-3-methyl-6dibutylaminofluorane as the leuco dye and isocyanate (Coronate manufactured by Nippon Polyurethane Co., Ltd.) were added to the dispersion obtained by pulverizing and dispersing the reversible developer. HL) 5 parts by mass was added and stirred well to prepare a thermoreversible recording layer coating solution.
The obtained thermoreversible recording layer coating solution was applied onto the first oxygen barrier layer using a wire bar, dried at 100 ° C. for 2 minutes, and then cured at 60 ° C. for 24 hours. A first thermoreversible recording layer having a thickness of 6.0 μm was formed.

-Formation of photothermal conversion layer-
4 parts by mass of a 1% by mass solution of a phthalocyanine-based photothermal conversion material (manufactured by Nippon Shokubai Co., Ltd., IR915, absorption peak wavelength: 956 nm), 10 parts by mass of an acrylic polyol 50% by mass solution (hydroxyl value = 200 mgKOH / g), and methyl ethyl ketone 20 5 parts by mass of isocyanate (trade name: Coronate HL, manufactured by Nippon Polyurethane Co., Ltd.) as a mass part and a crosslinking agent were thoroughly stirred to prepare a photothermal conversion layer coating solution. The obtained coating solution for the photothermal conversion layer was applied onto the first thermoreversible recording layer using a wire bar, dried at 90 ° C. for 1 minute, and then cured at 60 ° C. for 24 hours. A photothermal conversion layer having a thickness of 3 μm was formed.

-Formation of second thermoreversible recording layer-
The same composition for a thermoreversible recording layer as the first thermoreversible recording layer is applied onto the photothermal conversion layer using a wire bar, dried at 100 ° C. for 2 minutes, and then at 60 ° C. for 24 hours. Curing was performed to form a second thermoreversible recording layer having a thickness of 6.0 μm.

-Formation of UV absorbing layer-
Add 10 parts by weight of a 40% by weight UV-absorbing polymer solution (manufactured by Nippon Shokubai Co., Ltd., UV-G300), 1.5 parts by weight of isocyanate (manufactured by Nippon Polyurethane Co., Ltd., Coronate HL), and 12 parts by weight of methyl ethyl ketone, and stir well. Thus, a coating solution for an ultraviolet absorbing layer was prepared.
Next, on the second thermoreversible recording layer, the ultraviolet absorbing layer coating solution was applied with a wire bar, heated and dried at 90 ° C. for 1 minute, and then heated at 60 ° C. for 24 hours. An ultraviolet absorbing layer having a thickness of 1 μm was formed.

-Formation of second oxygen barrier layer-
The same silica-deposited PET film with an oxygen barrier layer as the first oxygen barrier layer was bonded onto the ultraviolet absorbing layer and heated at 50 ° C. for 24 hours to form a second oxygen barrier layer having a thickness of 12 μm.

-Formation of back layer-
Pentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd., KAYARAD DPHA) 7.5 parts by mass, urethane acrylate oligomer (manufactured by Negami Kogyo Co., Ltd., Art Resin UN-3320HA) 2.5 parts by mass, acicular conductive titanium oxide ( FT-3000 manufactured by Ishihara Sangyo Co., Ltd., long axis = 5.15 μm, short axis = 0.27 μm, composition: 2.5 parts by mass of titanium oxide coated with antimony-doped tin oxide, photopolymerization initiator (Nippon Ciba-Geigy Corporation) Manufactured, Irgacure 184) and 0.5 parts by mass of isopropyl alcohol and 13 parts by mass of isopropyl alcohol were added, and the mixture was thoroughly stirred with a ball mill to prepare a coating solution for a back layer.
Next, the back layer coating solution is coated with a wire bar on the surface of the support on which the first thermoreversible recording layer or the like is not formed, and heated and dried at 90 ° C. for 1 minute. After that, it was crosslinked with an 80 W / cm ultraviolet lamp to form a back layer having a thickness of 4 μm. Thus, the thermoreversible recording medium in Production Example 1 was produced.

(Production Example 2)
<Manufacture of thermoreversible recording medium>
In Production Example 1, lanthanum boride, which is a photothermal conversion material, was added to the thermoreversible recording layer coating solution so as to have the same sensitivity as the photothermal conversion material of Production Example 1, and the first thermoreversible recording layer having a thickness of 12 μm. The thermoreversible recording medium of Production Example 2 was produced in the same manner as in Production Example 1, except that the second thermoreversible recording layer, the photothermal conversion layer, and the second barrier layer were not formed.

(Example 1, Example 2, and Comparative Example 1)
As Comparative Example 1, a circular beam by the conventional image erasing apparatus (laser marker using fiber coupled LD) shown in FIG. 1, and as Examples 1 and 2, the image erasing apparatus (LD array light source) of the present invention shown in FIG. In Example 1, a Fresnel lens is used as the lens 15, and in Example 2, a convex lens array is used as the lens 15, and thermoreversible recording in Production Example 1 is used. The erase energy and erase width when the solid image recorded on the medium was erased were measured as follows. The results are shown in Table 1 and FIG. FIG. 9 shows the results of Example 1 (line light source erasure) and Comparative Example 1 (circular beam erasure).
In Comparative Example 1, laser beam irradiation was performed with a Xt Corbus FB100-980-35-01 (center wavelength: 976 nm) of a fiber-coupled LD (semiconductor laser) manufactured by Spectra-Physics Co., Ltd. as an eraser using a circular beam of a conventional image erasing apparatus. This is a device that collimates light with two collimator lenses (focal length 26 mm), scans the laser light with a galvano scanner 6230H manufactured by Cambridge, and focuses it with an fθ lens (focal length 141 mm). An area of 40 mm × 40 mm was erased with an overlap pitch width of 0.60 mm by a laser beam scanning method shown in FIG. 10 at 180 mm (circular, beam diameter 3.0 mm), scanning linear velocity 1,000 mm / s.
In Examples 1 and 2, as an eraser using a line beam of the image erasing apparatus of the present invention, an LD light source JOLD-55-CPFN-1L-976 with a collimator lens of an LD bar light source manufactured by Jena Optics Co., Ltd. (center) The optical system lens shown in FIG. 7 is assembled using a wavelength of 976 nm and an output of 55 W, and adjusted to be a linear beam having a length of 40 mm and a width of 0.35 mm on a thermoreversible recording medium. A line-shaped laser beam was scanned with a Galvano Scanner 6230H manufactured by the company. A region of 40 mm × 40 mm was erased by scanning at a scanning line speed of 20 mm / s by the scanning method shown in FIG.

<Measurement of erase energy and erase width>
With the circular beam of the conventional image erasing apparatus of Comparative Example 1, the distance between the workpieces is 141 mm, the scanning linear velocity is 2500 mm / s, and the solid image density is 1.40 with a pitch width of 0.60 mm by the laser beam scanning method shown in FIG. The solid image was erased while changing the irradiation power by the image erasing method, and the erasing energy and erasing width at which the difference from the background density was 0.020 or less were obtained.
The erasing energy is defined as the erasable energy that is the irradiation energy of the laser beam when the background density after erasing the solid image is +0.02 or less than the background density before forming the solid image. It is defined as the average value of the maximum and minimum possible energy. The erase width is defined as (maximum value−minimum value) / (maximum value + minimum value). In addition, the density | concentration measurement was measured with the reflection densitometer (the X-rite company make, 938 Spectro-Densido-meter).

  From the results shown in FIG. 9 and Table 1, the image erasing apparatus according to the first and second embodiments of the present invention can be erased with a line beam with lower energy than the conventional image erasing apparatus of Comparative Example 1 with a circular beam. It was found that it is possible to erase. The result is considered to be the effect of reducing the energy loss due to thermal diffusion by using a linear beam. Furthermore, compared with Example 1, Example 2 can secure a wider erase width and has higher erasability. This is because the light distribution uniformity in the long axis length direction can be improved.

<Evaluation of erase time>
Next, a 40 mm × 40 mm region recorded on the thermoreversible recording medium of Production Example 1 with a circular beam by the conventional image erasing apparatus of Comparative Example 1 and a line beam by the image erasing apparatus of the present invention of Example 1 was used. The erasing time of the solid image at an irradiation power of 30 W was measured. The results are shown in Table 2.

From the results shown in Table 2, in the line beam by the image erasing apparatus according to the first and second embodiments of the present invention, in addition to being erasable with low energy, jumping by laser beam scanning (laser beam scanning without irradiating laser beam) (See FIG. 10), it is not necessary to perform erasing, and the erasing time is not extended by jumping. Thus, it was found that erasing can be performed in a short time with the same irradiation power (erasing energy is reduced by 12%, erasing). 24% decrease in time).

<Evaluation of background coloring (background fogging) by repeated erasing>
Next, the influence of the background coloring (background fogging) due to repeated erasure is as follows using the circular beam by the conventional image erasing apparatus of Comparative Example 1 and the line beam by the image erasing apparatus of the present invention of Examples 1 and 2. Evaluation was performed as described above.

-Evaluation method of background coloring (background fogging) after repeated erasing-
Only the background portion of the thermoreversible recording medium of Production Example 1 where no image was recorded was repeatedly erased, and the number of repetitions immediately before the difference from the background density was greater than 0.020 was determined. At this time, the erasing energy was set as an average value of the maximum value and the minimum value of erasable energy. Moreover, the density | concentration measurement was measured with the reflection densitometer (The X-rite company make, 938 Spectro-Densido-meter).

  As a result, when repeated erasing is performed, the density of the background portion is increased, and the limit of 0.02 with respect to the initial background density is 400 times with the circular beam by the conventional image erasing apparatus of Comparative Example 1, In the line beam by the image erasing apparatus of the first embodiment of the present invention, the number of improvements was 5,000 times. This is considered to be because the line beam by the image erasing apparatus of the present invention of Example 1 does not need to be overlapped by scanning with laser light.

  Next, in the image erasing apparatus of the present invention of Example 2, the erasing energy and erasing width were measured by changing the short axis length of the line beam by changing the focal length of the cylindrical lens 3. The results are shown in Table 3.

From the results in Table 3, it can be seen that, in the line beam by the image erasing apparatus of the present invention of Example 2, the erasing energy and the erasing width can be controlled by controlling the beam width. It was found that by controlling the beam width accordingly, erasing can be performed in accordance with erasability.

(Example 3)
In Example 2, in the image erasing apparatus of the present invention shown in FIG. 7, a stepping motor mirror is attached in place of the galvanometer mirror, and scanning of the stepping motor mirror is controlled to scan at a scanning linear velocity of 20 mm / s. When the solid image was printed and erased in the same manner as in Example 2, the solid image could be completely erased (the density difference between the erased portion and the background portion was 0.00).

Example 4
In Example 2, in the image erasing apparatus of the present invention shown in FIG. 7, except that the polygon mirror is attached instead of the galvanometer mirror and the rotation speed of the polygon mirror is adjusted so as to scan at a scanning linear velocity of 20 mm / s, When the solid image was printed and erased in the same manner as in Example 2, the solid image could be completely erased (the density difference between the erased portion and the background portion was 0.00).

(Example 5)
In Example 2, the galvanometer mirror in the image erasing apparatus of the present invention shown in FIG. 7 is removed, and solid image printing is performed on the thermoreversible recording medium of Production Example 1 in the same manner as in Example 2, and the thermoreversible recording is performed. When the medium was affixed to a plastic box and placed on a conveyor and erased while moving the box at a transport speed of 20 mm / s (1.2 m / min), the solid image could be completely erased (the eraser and The density difference from the background was 0.00).

(Example 6)
In Example 2, when the solid image printing and erasing were performed on the thermoreversible recording medium of Production Example 2 in the same manner as in Example 2 in the image erasing apparatus of the present invention shown in FIG. 7, the solid image was completely erased. (The density difference between the erased portion and the background portion was 0.00).

  In the image erasing method and the image erasing apparatus of the present invention, the laser beam can be scanned only in one axial direction, and high-speed erasing can be performed with low energy, and the apparatus cost can be greatly reduced. It can be widely used for stickers for food containers, industrial products, various chemical containers, etc., for large screens such as logistics management applications and manufacturing process management applications, and for various displays. In particular, process management in logistics / distribution systems and factories It is suitable for system use.

DESCRIPTION OF SYMBOLS 1 Semiconductor laser array 2 Width direction parallelization means 3 Cylindrical lens 1 (Beam width adjustment means of the width direction)
4 Spherical lens 1 (length and width beam width adjusting means)
5 Scanning means 6 Spherical lens 2 (length and width beam width adjusting means)
7 Beam size adjusting means 8 Cylindrical lens 2 (beam width adjusting means in the width direction)
DESCRIPTION OF SYMBOLS 9 Long axis length direction light distribution control means 10 Thermoreversible recording medium 11 Special optical system 12 Optical fiber 13 1st cylindrical lens 14 2nd cylindrical lens 15 Laser beam diffusion lens of length direction

JP 2004-265247 A Japanese Patent No. 3998193 Japanese Patent No. 3161199 Japanese Patent Laid-Open No. 9-30118 Japanese Patent Application Laid-Open No. 2000-136022 JP-A-11-151856 Japanese Patent No. 4263228 JP 2008-62506 A JP 2008-213439 A Japanese Patent No. 3256090 JP 2008-137243 A JP-A-10-92729 JP 2002-353090 A

Claims (15)

A semiconductor laser array in which a plurality of semiconductor laser light sources are linearly arranged;
A width direction collimating unit disposed on the emission surface of the semiconductor laser array and configured to parallelize the spread in the width direction of the laser beam emitted from the semiconductor laser array;
The long axis length of the linear beam formed by the width direction collimating means is longer than the long axis length of the light emitting part of the semiconductor laser array and has a uniform light distribution in the long axis length direction. A direction light distribution control means,
A linear beam having a light distribution that is longer than the long axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the long axis length direction is reversibly changed in temperature or transparency depending on temperature. An image erasing apparatus for erasing an image recorded on a thermoreversible recording medium by irradiating and heating the reversible recording medium.   Beam size adjusting means for adjusting at least one of a major axis length and a minor axis length of a line beam having a uniform light distribution in the major axis length direction and longer than the major axis length of the light emitting portion of the semiconductor laser array The image erasing apparatus according to claim 1, comprising:   The image erasing apparatus according to claim 1, wherein the width direction parallelizing means is a cylindrical lens.   4. The image erasing apparatus according to claim 1, wherein the long axis length direction light distribution control means is a lens array.   4. The image erasing apparatus according to claim 1, wherein the long axis length direction light distribution control means is a Fresnel lens.   2. A scanning means for scanning in a uniaxial direction a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and uniform in the major axis length direction on the thermoreversible recording medium. 6. The image erasing apparatus according to any one of items 1 to 5.   The image erasing apparatus according to claim 6, wherein the scanning unit is a uniaxial galvanometer mirror.   The image erasing apparatus according to claim 6, wherein the scanning unit is a stepping motor mirror.   The image erasing apparatus according to claim 6, wherein the scanning unit is a polygon mirror.   A thermoreversible recording medium is moved by a moving means with respect to a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and uniform in the major axis length direction. 10. The image erasing apparatus according to claim 1, wherein the line-shaped beam is scanned to erase an image recorded on the thermoreversible recording medium.   The image erasing apparatus according to claim 10, wherein the thermoreversible recording medium is attached to the surface of the container, and the thermoreversible recording medium is moved by moving the container by a moving unit. A width-direction parallelizing step for parallelizing the spread in the width direction of the laser light emitted from the semiconductor laser array in which a plurality of semiconductor laser light sources are arranged linearly;
The long axis length of the linear beam formed in the parallelizing step in the width direction is longer than the long axis length of the light emitting portion of the semiconductor laser array and makes the light distribution uniform in the long axis length direction. Directional light distribution control process;
Comprising at least
A linear beam having a light distribution that is longer than the long axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the long axis length direction is reversibly changed in temperature or transparency depending on temperature. An image erasing method comprising erasing an image recorded on a thermoreversible recording medium by irradiating and heating the reversible recording medium.   A beam size adjusting step for adjusting at least one of a major axis length and a minor axis length of a line beam having a uniform light distribution in the major axis length direction and longer than the major axis length of the light emitting portion of the semiconductor laser array The image erasing method according to claim 12.   14. A scanning step of scanning in a uniaxial direction a linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and uniform in the longitudinal direction on the thermoreversible recording medium. The image erasing method according to any one of the above.   The thermoreversible recording medium is moved by a moving means with respect to the linear beam having a light distribution that is longer than the major axis length of the light emitting portion of the semiconductor laser array and has a uniform light distribution in the length direction. The image erasing method according to claim 12, wherein an image recorded on the thermoreversible recording medium is erased by scanning a line beam.